A common method for determining a refraction is the so-called subjective refraction determination, which is widely accepted by opticians. Conventionally, in the subjective refraction determination, the user of a spectacle lens is being presented different spectacle lenses, i.e. spectacle lenses with different optical properties, wherein the user of the spectacle lens informs the refractionist of an improvement or deterioration of the visual impression upon a change of the optical properties of the presented spectacle lens. The subjective refraction determination may e.g. be based on values of an objective refraction determination or on values of already worn spectacles. However, the accuracy of the subjective refraction determination critically depends on the skill of the refractionist, for example an optician and/or ophthalmologist, who performs the subjective refraction determination. Likewise, the subjective refraction determination also critically depends on the person to be examined, in particular on the ability of the person to be examined to assess and/or express the sharpness of the visual impressions.
Often, measuring methods for determining the subjective refraction differ strongly depending on the college of ophthalmic optics, and are also different on an international level. Thereby, greater differences in the results occur.
Furthermore, since the individual refraction lenses are only available in steps of maximally approx. 0.125 D, usually only approx. 0.25 D, the maximum (theoretical) accuracy is usually also only 0.125 D.
In addition, the subjective refraction is only performed with one contrast strength, usually with the maximum contrast and the lowest resolution. It is not checked whether the determined refraction values also represent the ideal refraction values in the case of a bad contrast and a low resolution.
The refraction determination is only performed with one pupillary size, usually with a strong illumination and a small pupil. It is not checked whether the refraction varies along with the pupillary size.
Moreover, the ambient parameters may sometimes vary very strongly depending on the examination location, and have a significant, uncontrollable influence on the result. The ambient parameters are e.g. contrast of the eye test, distance of the eye test, size of the optotypes, shape of the optotypes, and room brightness. Therefore, the subjective refraction often only provides results far from satisfactory.
It is therefore an object of the present invention to provide refraction data of a user of a spectacle lens in a simple manner.
This object is achieved by the method, by the computer program product, and by the apparatus of the independent claims. Preferred embodiments are subject of the dependent claims.
Method According to One Aspect of the Invention
One aspect of the present invention relates to a method for checking and/or determining user data of a spectacle lens user, comprising the steps of:                providing subjective data of a spectacle lens user, wherein the subjective data at least comprise subjective refraction data;        providing objective refraction data of the spectacle lens user;        comparing at least a subset of the subjective refraction data with at least a subset of the objective refraction data, and determining a comparative result;        matching at least the subset of the subjective refraction data to the objective refraction data on the basis of the comparative result provided that the comparative result fulfils at least one predetermined comparative condition, otherwise, maintaining at least the subset of the subjective refraction data and/or        providing a message containing the comparative result.        
Advantageously, the subjective refraction measurement and the objective refraction measurement are combined with each other. For example, deviations between the subjective and the objective refraction may occur due to adaptations of the visual system. These deviations can be easily and safely be determined and be compensated for if need be. In particular, it may advantageously be checked whether the determined refraction values are physiologically compatible with the future users. For example, it often happens that the “perfect” imaging, i.e. an imaging according to objective refraction data, is subjectively not considered to be the best, since the visual system has already adapted to the faulty refraction in sensoric terms. For example, if the user has a slight hyperopia, the user can compensate for this hyperopia by means of accommodation as long as he/she is not presbyopic. If e.g. such a hyperopia is fully corrected on the basis of the objective refraction data, this may lead to incompatibility. The same applies to astigmatic visual defects. In this case, however, the difference between subjective and objective refraction data may be even more significant. For example, a full correction on the basis of objective refraction data may subjectively not be considered to be the best correction. However, according to the present invention, it is possible to determine e.g. (significant) deviations of the subjective refraction data from the objective refraction data and to thereby find out whether the refractionist has performed a faulty refraction determination. If need be, the subjective refraction data can be matched to the objective refraction data at least partially. Additionally or alternatively, the values obtained by the subjective refraction measurement can be maintained for at least a part of the refraction data even if these values deviate from the objective refraction data. In particular, a comparative condition can be set, wherein no adaptation of the subjective refraction data is made if the difference between the objective refraction data and the subjective refraction data is less than the comparative condition. As an example, a maximum deviation of the spherical refractive power, the astigmatism, in particular the axial position of the astigmatism, etc., may be set or predetermined and, as long as the deviation is smaller than the maximum predetermined deviation, no adaptation of the subjective refraction data is made. As a further example, a maximum value of the sphere and/or the cylinder of the deviation, calculated according to the cross-cylinder method, between the subjective and the objective refraction data may be set. In both cases, the maximally admissible deviation may be 0.1 D, 0.2 D, 0.5 D, 1 D, 2 D, etc. In other words, the comparative condition may correspond to the maximally admissible deviation. The maximum deviation may as well be a relative value, for example one percent. The maximum deviation, i.e. the comparative condition, may be a difference between an objective and a subjective value (or several such values) between approx. 1% and approx. 50%, in particular between approx. 10% and approx. 30%, e.g. also a deviation of approx. 1%, 2%, 3%, 5%, 10%, 15%, 20%, 25%, etc.
Alternatively or in addition, a message containing the comparative result may be output. In particular, the message may be a warning message, which indicates that e.g. a subset of the subjective refraction data and a subset of the objective refraction data do not meet a predetermined comparative condition, i.e. that a deviation of at least a subset of the subjective refraction data from the corresponding objective refraction data is present which is e.g. greater than a predetermined comparative condition. In a next step, the refractionist may e.g. manually change the subjective refraction data, in particular match them to the objective refraction data. The refractionist may as well repeat the subjective refraction determination at least partially. It is also possible to automatically match the subjective refraction data to the objective refraction data.
The term “providing” as defined by the present invention includes “measuring”, “estimating”, “transferring”, “taking from a database and/or a table”, “sending”, etc.
The subjective data include at least subjective refraction data. The subjective data may also include further data, such as the age of the spectacle lens user, a development of the visual defect of the spectacle lens user, a medical history of the spectacle lens user, etc.
The subjective data may be collected e.g. by an optician, an ophthalmologist, etc. The subjective data may also be available from a local database or one incorporated in a network, or from a server-based database, or an external database, etc. This data may be completed with the subjective refraction data or the subjective refraction data may be renewed after refraction determination. For example, the subjective data may be transferred to a spectacle lens manufacturer. This transfer may be by mail, for example. The subjective data may as well be transferred via a network, for example the Internet, etc.
Also, the objective refraction data may be taken from a database and be updated by the optician, the ophthalmologist, etc. The objective refraction data may (subsequently) be transferred to a spectacle lens manufacturer.
The objective refraction data and/or at least a subset of the subjective data may also be deposited with the spectacle lens manufacturer.
Moreover, the comparison of at least the subset of the subjective refraction data with at least the subset of the objective refraction data may be performed at the optician, ophthalmologist, etc., and likewise, comparative results may be output there and at least a subset of the subjective refraction data be adapted if need be. Alternatively or in addition, the comparison, optionally the adaptation and/or the outputting of the message may also take place at the spectacle lens manufacturer.
Matching at least the subset of the subjective refraction data to the objective refraction data may in particular include changing one or more values of the subjective refraction data. For example, a value of the subjective refraction data, which deviates from a value measured by means of objective refraction, may be matched to the value determined by objective measurement. The value of the subjective refraction measurement may e.g. be equated with the value of the objective refraction measurement. The value of the subjective refraction measurement may as well be equated with the average value of the subjective and the objective refraction value. It is also possible for the subjective refraction value to be increased or decreased by 5%, 10% or 15%, 20%, etc., of the difference of the value of the subjective refraction measurement and the objective refraction measurement.
By means of the combination of the subjective refraction data and the objective refraction data, in particular by means of the possible selective change of subjective refraction data and/or by maintaining the subjective refraction data, also if they deviate from the objective refraction data, an intended deviation of the subjective refraction data from the objective refraction data in particular due to geometrical-optical imaging differences may advantageously be maintained. Such imaging differences may occur due to the distance spectacle lens-eye in particular in a correction of astigmatic visual defects, since a strange distortion may be present owing to the distance spectacle lens-eye. Since also in this case a full correction according to objective refraction data is often subjectively not considered to be the best correction, it may be advantageous to not match the subjective refraction data or only a subset of the subjective refraction data to the objective refraction data. It is also possible to only match the subjective refraction data to the objective refraction data e.g. by a few percentage points (1%, 2%, 3%, 5%, 10%, etc.). Thus, the influence of geometrical-optical imaging differences can advantageously be taken into account.
Further preferably, by means of the combination of subjective and objective refraction measurements, binocular vision can be taken into account, which is particularly neglected in conventional objective measuring methods. Here, binocular vision has a great influence on the refraction values due to the strong coupling of accommodation and convergence. In the case of exophoria, a divergence excess and/or a convergence insufficiency, often great differences between the monocular and binocular refraction values occur. For example, binocular values shift toward minus, since with the therefor required accommodation and the resulting convergence, the exophoria, i.e. a two-part, outward deviation of the visual axis, is compensated for. Conversely, in the case of esophoria, a divergence insufficiency or convergence excess, i.e. inward strabismus, the values often shift toward plus. In a subjective refraction determination, these influences can be taken into account, since in particular the subjective refraction determination is possible in a binocular manner. By correspondingly adapting the comparative conditions, the subjective refraction data and the objective refraction data can be compared with each other, and for example a deviation of the subjective refraction data from the objective refraction data may be allowed due to the binocular subjective refraction measurement.
Further advantageously, in particular due to a schematic approach in a subjective refraction determination, accommodation may be controlled or taken into account. It is often difficult to determine the influence of accommodation on an objective refraction measurement, or it cannot be taken into account.
Preferred Variants of the Method
According to a preferred variant, target values of at least one spectacle lens are determined on the basis of the following data:                at least a subset of the subjective refraction data and/or        at least a subset of the adapted subjective refraction data and/or        at least a subset of the objective refraction data.        
The term “determining” as defined by the present application includes calculating or estimating at least one target value. For example, on the basis of the predetermined data, a target value may be taken from a database and/or be calculated by means of predetermined optimisation algorithms. Here, one or more optimisation methods may be used.
The term “target value” as defined by the present application includes a desired value of a spectacle lens. In other words, the target value of the spectacle lens is the value corresponding to the defaults set by an optician, an ophthalmologist and/or a manufacturer. The target value may comprise several values. The target value may in particular include values for the spherical power, cylinder, axis, etc., which the spectacle lens is to have. In an ideal spectacle lens, the actual optical properties correspond to the target value.
Further preferably, the subjective refraction data and/or the matched subjective refraction data and/or the objective refraction data are combined to form combined refraction data.
Here, the subjective refraction data may be the refraction data provided by subjective refraction measurement. The matched subjective refraction data may e.g. be the subjective refraction data matched on the basis of the objective refraction data, or a subset of these subjective refraction data. The objective refraction data are the objective refraction data provided by means of an objective method.
In particular, a subset or a total of the aforementioned data may be used. For example, target values may be determined on the basis of combined objective refraction data formed by combination of                at least a subset of the subjective refraction data and/or        at least a subset of the matched subjective refraction data and/or        at least a subset of the objective refraction data.        
Further preferably, effective objective refraction data are generated on the basis of at least a subset of the objective refraction data, wherein for determining the comparative results, the effective objective refraction data are compared with at least a subset of the subjective refraction data. For example, a variety of objective refraction data may be generated among others for a variety of pupillary sizes, different boundary conditions, such as brightness, contrast, etc., and the effective objective refraction data may be generated or determined on the basis of this variety of objective refraction data. For example, it is possible that merely a part of the objective refraction data is changed to form effective objective refraction data. The rest of the objective refraction data remains unchanged. The total of these effective objective refraction data and of the remaining objective refraction data may be referred to as effective objective refraction data. These effective objective refraction data may be compared with the subjective refraction data.
For example, it is possible to determine target values on the basis of combined objective refraction data formed by combination of                at least a subset of the subjective refraction data and/or        at least a subset of the matched subjective refraction data and/or        at least a subset of the objective refraction data.        
According to a further preferred embodiment, several sets of objective refraction data are provided, and the effective objective refraction data are generated on the basis of the several sets of objective refraction data. The sets of objective refraction data may e.g. be generated for different boundary conditions (see above).
For example, the effective objective refraction data are determined taking the following boundary conditions into account:                brightness and/or        pupil diameter and/or        contrast and/or        age.        
Preferably, for calculating the effective objective refraction data, an aberration function or wave function and/or an optical transfer function (referred to as “OTF”) and/or a modulation transfer function (referred to as “MTF”) and/or a so-called point spread function (referred to as “PSF”) and/or a standard deviation and/or a Strehl ratio are calculated. In this connection, reference is made to the relevant literature. Precise definitions of the aberration function are e.g. found in the book “Principles of Optics” by Born and Wolf, Pergamon Press (1980), pages 203 ff. and pages 459 ff. A definition of the Strehl ratio is given on pages 462 ff. Definitions of “OTF” and “MTF” as well as a discussion thereof are given in the book “Introduction to Fourier Optics” by Goodman, McGraw-Hill, 1968. The point spread function (“PSF”) is the Fourier transform of the “OTF” and is the point image function, i.e. describes the intensity distribution of the image which an optical systems forms from a point-shaped light source. PSF is e.g. defined and explained in the “The eye and visual optical instruments”, by Smith/Atchison, Cambridge University Press, 1996.
Particularly preferably, an aberration function is taken into account, wherein the considered order of the aberration is variable.
In other words, the order of the aberration can be selected once and be maintained then. It is also possible to change the order of the aberration continuously or stepwise or iteratively, etc.
According to a further preferred embodiment, at least a subset of the objective refraction data is determined by means of eccentric photorefraction.
In particular, at least the subset of the objective refraction data may be determined in a monocular or binocular manner.
Method According to a Further Aspect of the Invention
A further aspect of the present invention relates to a method for checking and/or determining user data of a spectacle lens wearer, comprising the steps of:                providing objective refraction data of the spectacle lens user;        determining effective objective refraction data, wherein the effective objective refraction data are generated on the basis of at least a subset of the objective refraction data; and        determining target values of at least one spectacle lens on the basis of the effective objective refraction data.        
Further, with respect to this method, the aforementioned preferred variants and the aforementioned advantages analogously apply as well.
Further preferably, at least one of the aforementioned methods comprises the step of:
manufacturing the at least one spectacle lens on the basis of the determined target values.
Computer Program Product According to One Aspect of the Invention
A further aspect of the present invention relates to a computer program product, in particular stored on a computer-readable medium or realized as a signal, which, when loaded into the memory of a computer and executed by a computer, causes the computer to execute an inventive method.
Apparatus According to One Aspect of the Invention
A further aspect of the present invention relates to an apparatus for checking and/or determining user data of a spectacle lens user, comprising:                a subjective data providing device adapted to provide subjective data of a spectacle lens user, wherein the subjective data comprise at least subjective refraction data;        an objective data providing device adapted to provide objective refraction data of the spectacle lens user;        a comparing device adapted to compare at least a subset of the subjective refraction data with at least a subset of the objective refraction data, and adapted to determine a comparative result;        a matching device adapted to match at least the subset of the subjective refraction data to the objective refraction data on the basis of the comparative result provided that the comparative result fulfills at least a predetermined comparative condition, wherein the matching device is adapted to otherwise maintain at least the subset of the subjective refraction data and/or        wherein the comparing device is adapted to provide a message containing the comparative result.Apparatus According to a Further Aspect of the Invention        
A further aspect of the present invention relates to an apparatus for checking and/or determining user data of a spectacle lens user, comprising:                an objective data providing device adapted to provide objective refraction data of a spectacle lens user;        a determining device adapted to determine effective objective refraction data, wherein the effective objective refraction data are generated on the basis of at least a subset of the objective refraction data;        a determining device adapted to determine target values of at least one spectacle lens on the basis of the effective objective refraction data.Preferred Embodiments of the Apparatuses        
Preferably, one of said apparatuses comprises a manufacturing device adapted to manufacture at least one spectacle lens on the basis of the determined target values.
Further preferably, the aforementioned explanations and advantages with respect to the methods analogously also apply to the aforementioned apparatuses. In particular, the aforementioned apparatuses have means or devices adapted to perform the aforementioned method steps.